Hydrodynamic Performance Analysis And Optimization Of Offshore Wind Turbine Semi-submersible Platform

For the sustainable development of mankind,countries around the world have carried out a lot of research in the field of renewable energy.Offshore wind power has received the attention of many countries because of its inherent advantages such as large wind energy reserves and fewer restrictions.The design of offshore wind turbine platforms is the key point of offshore wind farm construction.This paper introduces the two basic types of wind turbine foundation,fixed foundation and floating foundation.According to the future development direction of offshore wind power,the offshore semi-submersible wind power platform WindFloat was selected as the research object.The two main research methods: model test and numerical simulation are combined to analyze the hydrodynamic performance and dynamic characteristics of offshore wind power platform systematically.First of all,this paper adopts the model test scheme and tests the platform model in still water and regular waves.Through the free decay motion of the platform in still water,the basic parameters such as the natural frequency of the platform are obtained.In the regular wave test,the amplitude response operator of the platform heave,sway,and pitch motion is obtained,and the motion response characteristics of the platform under the two mooring states of three anchor chains and four anchor chains are analyzed and compared..Secondly,this paper establishes a numerical calculation model using commercial CFD software STAR-CCM+.Firstly,the grid and time step convergence are analyzed.Then the numerical calculation results are compared with the experimental data.The results are in good agreement,and the feasibility and accuracy of the numerical calculation model is verified.The numerical model is used to calculate the numerical simulation of the paper.The results show that the numerical results are more accurate under still water conditions,and there are certain numerical differences in the regular wave conditions,but the overall trend is consistent.At the same time,the systematic analysis of the difference between experimental data and calculation results was carried out.Then,the integrated damping plate platform designed by Guanqing Hu et al.is introduced to analyze the hydrodynamic performance and motion characteristics of the integrated damping plate platform and WindFloat platform under still,regular and irregular waves.Then the hydrodynamic performance and motion characteristics of the two platforms under static water,regular wave and irregular wave are analyzed.It is verified that thehydrodynamic performance of the newly designed integrated damping plate platform is better than that of the WindFloat platform.Finally,this paper introduced the three-dimensional potential flow software AQWA to establish the frequency domain and time domain calculation model with the viscosity correction to analyze the platform motion characteristics.The typical working conditions of the test were selected for calculation and comparison,and the results were in good agreement.Then based on the principle of control variables,the influence of wave angle,water depth,mooring line length and numbers of mooring lines on the motion characteristics of floating platform is analyzed.The results show that as the incident angle of the wave increases,the surge and pitch responses decrease,the roll response increases,and the heave response remains basically unchanged.As the cable length increases,the average value of the heave response and the amplitude of the heave response increase,and the average value of the heave displacement increases.The heave binding force of the mooring system decreases as the cable length increases,and the range of the surge and pitch restraining forces increases as the cable length decreases.The increase of water depth has obvious influence on the heave motion and the surge motion,but it has little effect on the pitch motion.An increase in the number of mooring lines can reduce the heave motion response of the platform.The three mooring lines and the six mooring lines show a similar trend of motion response at different wave angles due to the symmetry of the mooring system structure arrangement.However,the platform motion response has the lowest value with the six mooring lines.